In situ HREM: application to metal-mediated crystallization

In situ high-resolution electron microscopy (HREM) is applied to study the metal-mediated crystallization of amorphous semiconductors. The systems reported here are Ag-Ge and Ag-Si, prepared in trilayer form by sputtering. The observations show that the reaction occurs by nucleation within the metal, followed by diffusion through the solid metal layer with no formation of intermediate, metastable or liquid phases. The reaction temperatures in situ match well with those established by ex situ differential scanning calorimetry (i.e. 275°C and 415°C for the Ge and Si trilayers, respectively), and the measured growth rates provide an activation energy value (1.75 eV) which is consistent with a substitutional counter-diffusion mechanism. The significant benefits of the in situ HREM approach are illustrated by this work.